DE 10 2006 051 406 A1 of the applicant discloses a fuel filter as described above in which the cover is embodied as a housing head that is screwed onto the housing pot. The guide pipe ends in the housing head at a sealing plug that separates the interior of the guide pipe from the surrounding clean area. In case the sealing plug does not completely seal the clean area, it is possible that unpurified water/fuel mixture can pass from the guide pipe into the surrounding clean area.